My family has 8 (yes, you read that right) Newfies so I'd say I have a little experience with the breed. They are amazing dogs- intelligent, good-natured, easy going, and very chill. 1 of the 8 will be coming with me when I (hopefully) head off to vet school next year, and I'm not at all worried about how he'll do. He's such a calm dog I'm sure he'll be fine with whatever attention I can provide him.
A lot of what has been said so far about joint problems with Newfies is true. They are (obviously) giant breed dogs, and so their joints do have to take a lot of force. There are a lot of things you can do to avoid these issues though. Most important is to get a puppy from a quality breeder. Parents (and grandparents, great grandparents, aunts, uncles, etc, ideally) should all have been OFA tested for hips AND elbows. Pennhip is another option for hips, though I personally prefer OFA. Look for mostly OFA excellents and goods. Make sure you double check what the breeder says on their website too. Their are some dishonest breeders out there who will tell you their dogs have good hips, but they may not have been tested at all. If you go to the OFA website, you can search their registry by the dogs' registered names and see their official OFA results.
Once you have your pup, make sure you feed a giant breed puppy food. Slow growth is essential for these guys, and giant breed puppy foods have reduced protein content to help keep them growing at an approriate rate. We also supplement all of our dogs with glucosamine and MSM.
The type of exercise that you choose for your Newfy can also help protect their joints. Newfies are bred to be water dogs, and swimming is excellent exercise for them because it is low impact on their joints. A newfy isn't the best choice for a running partner, the impact is hard on them and they tend to be a little on the lazy side 🙂
It's also true that they have pretty intense grooming requirements. They are double coated and can get pretty matted if not kept brushed (especially if they are going swimming frequently). However, as long as you keep up on it it really isn't that bad. Remember that it is absolutely essential that you never shave a Newfy (or any double coated breed dog, for that matter) as it causes irreparable damage to the hair coat.
If you have any other specific questions about Newfies, please feel free to ask me! They are truly a fantastic breed of dog and I really enjoy them!